It is well known in the art to utilize PAR (parabolic aluminized reflector) lamps for general spot lighting applications. In particular, PAR 38 (those with a 4.75 inch face diameter) spot lamps have become exceptionally popular for short-to-medium-distance outdoor uses as well as indoors for display, decoration, accent, inspection, and downlighting applications. Examples of such spot lamps are manufactured and sold by the assignee of the instant invention under the product designations 75 PAR/SP, 150 PAR/SP, and 150 PAR/3SP. Typically, these lamps are of hardglass and include a medium skirt (screw-type) or side prong base at the rear thereof for connecting the lamp to the desired power source.
The beam produced by a PAR lamp is typically of substantially conical configuration and provides a substantially round pattern. This pattern changes to being oval or elliptical should the lamp be aimed at an acute angle with the light-receiving surface. These lamps also may possess a rated average life of from 2000 to 4000 hours (with many more recently introduced models exceeding this), operate readily from standard household current (120 volt) and produce a beam having an output typically ranging from about 700 to about 3300 lumens.
Prior spot lamps, such as those of the type PAR 38 variety, include a lens that has either a stippled or irregular lens surface typically obtained by shot or sand blasting. The stippled surface usually appears over substantially the total face of the lamp lens. The resultant light pattern from such a surface provides a generally undesired asymmetrical pattern which is a function substantially solely of the stipple density. Moreover, a further drawback of existing spot lamps of this type is that there is little or no control of the beam pattern.
In addition to the aforementioned drawbacks associated with the spot lamp lens, there are further problems associated with the spot lamp reflector. Prior spot lamps such as type PAR 38 spot lamps utilize a reflector having a multiple parabolic front (forward) section generated by the combination of three different radii portions, a middle section formed of a partial sphere and a heel or rear section that is also of a partial sphere. This prior art construction of a reflector, particularly when taken in combination with the described stippled lens, provides a relatively inefficient means of projecting the available light. This arrangement further provides a narrow latitude for beam pattern alteration and also an undesired, asymmetrical candlepower distribution.